Preparation of (4-hydroxy-3,5-dialkyl-benzyl) carboxylic acid esters

ABSTRACT

Compounds of the formula   ARE PREPARED BY REACTING A Mannich base   WITH A CARBOXYLIC ACID ESTER OF THE FORMULA   AND ARE STABILIZERS FOR ORGANIC MATERIALS AGAINST DETERIORATION BY OXYGEN, LIGHT AND HEAT. In the formulae, R1 and R2 is alkyl, R3 is -CN or -COOR4, and R4 is an alkyl, aralkyl, cycloalkyl, ether or thioether group.

United States Patent 1191 Eggensperger et al.

[ Apr. 15, 1975 i 1 PREPARATION OF (4-HYDROXY-3,5-DIALKYL-BENZYL) CARBOXYLIC ACID ESTERS [75] Inventors: Heinz Eggen'sperger, Gadernheim Bensheim; Volker Franzen, Heidelberg; Karl-Heinz Diehl, Bensheim; Wilfried Kloss, Kolmbach Bensheim. all of Germany [73] Assignee: Ciba-Geigy Corporation, Ardsley,

[22] Filed: Dec. 4, 1972 [21] Appl. No.: 311,543

Related US. Application Data [60] Division of Scr. No. 146,840 May 25. 1971. Pat. No. 3.830828. which is a continuation of Scr. No. 66l,l9l, Aug. 17. 1967. abandoned.

Primary E.\'aminerElbert L. Roberts Assistant E.raminerDolph H. Torrence Attorney, Agent, or FirmFisher, Christen & Sabol [57] ABSTRACT Compounds of the formula no 6H CH-COOR m 2 I 4 l are prepared by reacting a Mannich base with a carboxylic acid ester of the formula c14 cooR 3 and are stabilizers for organic materials against deterioration by oxygen, light and heat.

In the formulae, R and R is alkyl, R is -CN or COOR and R is an alkyl, aralkyl, cycloalkyl, ether or thioether group.

5 Claims, No Drawings This is a division of application Ser. No. 146,840 filed May 25, 1971, now U.S. Pat. No. 3,830,822, said application being a streamlinedcontinuation of application Ser. No. 661,191 filed Aug. 17, 1967, now abandoned.

This invention relates to novel stabilizers and a method for their preparation.

Said stabilizers have the formula wherein R and R are as above and R is alkyl, preferably a lower alkyl, with a carboxylic acid ester of the general formula COOP? 1 I I) R,

wherein R aridR, are as above. The reaction is carried out in the presence of a catalytic amount of an alkali metal base or an alkaline earth metal base, preferably an alkali or alkaline earth metal alcoholate, in an anhy- IABLE I a.-, m a-.-. ..w .-ww.-.s .-..M.. Stabi- R R R R a melting point, yield 1 izer 1 2 5 3 4 l l (7 Ji M- on f 'itJJ emi a, CN 4 I luv-tel a"! 'CH W i tertbutyl, COOR 1 CH,, 5 191-193 72 i; I 4 I i I -CH3 v y ,teyttbutyl; COOR 45 411443 14 liquid 84 te'rt.b t l..c ooa -cn liquid 5 09 drous inert organic solvent.

The preparation of Mannich bases from phenols, formaldehyde and secondary amines is known.

Suitable solvents are hydrocarbons, glycol ethers and 5 other high boiling ethers. Also alcohols R,OH can be used. We prefer to employ aromatic hydrocarbons.

A preferred mode of operation consists in refluxing one mole of the Mannich base with one mole of the carboxylic acid ester (malonic acid ester, cyanoacetic acid 10 ester) in the presence of 1 to g of alkali or alkaline earth metal alcoholate in about 1 liter of toluene, preferably in a nitrogen atmosphere, for 2 to 3 hours. After cooling, the catalyst is removed, e.g. by neutralization with diluted acid and extraction with water, the reac- 5 tion mixture is dried, the solvent is distilled off, and the residue is purified, e.g., by recrystallization. The yield is about 70 to 90 percent of the theory.

The smooth course of reaction could not be expected because it was known, e.g., from the book by H. Hellmann and G. Opitz on "alpha-Aminoalkylation (publ. by Verlag Chemie, Germany), p. 284, that phenol- Mannich bases can be C-alkylated,'e.g., with malonic acid esters, only when the ammonium salts of the phenol bases are used as starting material, wherey said ammonium salts are difficult to prepare.

The following examples for the preparation of the compounds (I), and for their use as stabilizer, are given for their sake of illustration and without intention of limiting the invention to the specific details disclosed:

EXAMPLE 1 Preparation of (4-hydroxy-3methyl-S-tert. butyl benzyl) malonic acid distearyl ester (Stabilizer ll) 22.1 g (0.1 mole) of (3-methyl-5-tert. butyl-4- .hydroxylbenzyl)-dimethylamine were refluxed with 60.9 g (0.1 mole) of malonic acid distearyl ester and l g of magnesium ethylate in 75 cc of toluene for 3 hours under nitrogen. the solution was then cooled and filtered from the magnesium ethylate; subsequently, the toluene was distilled off in vacuo, and the residue was recrystallized from acetone. There were obtained 71 g of (4-hydroxy-3-methyl-5-tert. butyl benzyl) malonic acid distearyl ester in a yield of 90 per cent oftheory.

determined on the basis of the IR spectra and by quantitative analysis.

TABLE I-Continued x v Stabi- R R R R melting point yield lizer c 1 2 t g i f" 1 r 3 i -ca t.ert.butyli 0009. i x a} I 1 .tq id I: it l 1 l l i t j s -CH E tert .butyl t-Ccll -Cl-[ CH C H C0 C2 7.: i l l l l l I -CH terl .butyl; 0003 -C H 40-42 l 92 I a i 1 II CH tert.hutyl.| CCJCL 69 71 g 90 t I i i a 111 itert .butyl tert.butyl; COCK -CH CH SC, H & 37-40 i 74 3 IV lterhbutyl 'l'ex't .butyli CCOR i k! 65-08 I 89 l l 3'? l I i i a i Q, O V isopropyi lSOPIOPYl CCCP 0 1-1 i be 8 i The compounds of formula I are good antioxidants R and light and heat stabilizers for organic compounds, particularly for polymeric compounds such as polyole- HO 4431 fins, polyamides, shock-resistant polystyrene- R containing butadiene-styrene polymers, ABS polymers 2 (copolymers of acrylonitrile, butadiene, and styrene),

vegetable and animal oils and fats, plasticizers such as phthalates, and mineral oils.

Particularly good stabilizers are those of the formula in which R, has the significance given above and contains a total of 4-20 C atoms.

Generally, we prefer esters of higher alcohols, partic ularly those which containsulfur in ether linkage. Such esters are compatible with polymeric resins, fats and mineral oils and exert, due to their low volatility, a good stabilizing effect on these materials even afterprolonged thermal stresses.

Generally, the stabilizers are used in an amount of 0.01 to 10 percent, calculated on the total weight of the material to be stabilized.

As the following examples, particularly example 5, show, our novel stabilizers have an improved stabilizing effect when compared with known purely organic stabilizers such as the mixtures of alkylated phenols (German DAS 1,035,137) thiobisphenols, and w-(hydroxyalkyl-phenyl)-alkane carboxylic acid esters (German DAS 1,201,349). In contrast to the experience stated in the German DAS 1,201,349, in our stabilizers the character and number of the methylene groups which are between the carboxylate group, and the aromatic ring have considerable influence.

The new compounds can also be prepared by reacting benzyl halides of the formula with alkali metal (eg sodium) derivatives of carboxylic acid esters of the formula A1K-cH-cooR or by reacting 2,6-alkylated phenols with halogenated carboxylic acid esters of the formula Hal ca cooR EXAMPLE2 v 7 Stabilization of Polypropylene.

Two unstabilized polypropylene powders of melting index 1,6 of different origin (called A and B in Table II) were used. To parts by weight of said powders, the stabilizers listed in Table II were added. All mixtures were treated for 10 minutes at 180C on a laboratory roll mill, and the obtained films were pressed at 200 atm. and at a temperature of 210C. From the obtained 1 mm thick sheets, 5 strips were cut out and subjected by storage in a drying cabinet at C to an accelerated ageing; the time was determined after which an oxidative decomposition could be observed by the brittle test.

TABLE II I 100 parts weight of polyamide (Nylon 6,6) each I were mixed with the stabilizers listed in Table IV and o Polypropylene Smbilizer Brime Tesl I extruded at 250C to sheets from which samples were (pans by weight) (days) cutand sub ected to accelerated ageing in a drying cab- '5inetatl40 C. A 0.5 stabtllz r l 38 v The stabilizing effect was determined by the brittleslabfllzevram I 38 ness of the samples. As will be seen from Table IV, the

A 0.5 stabilizer Ill 66 B 0.2 Stabilizer L a l 49 stabilizers of the invention exceed the effect of prior art 3 DLTDp antioxidants. Addition of phosphite improves consider- B 0.2 stabilize gM 57 ably the early color of the extruded sheets 0.3 DLTDP: 1 I

B 0:2 stabilizerll I H TABLE 0.3 DLTDP I 1 Test Stabilizer Brittle after Stabilizer L 4,4'-thiobis-(6-tert.butyl-m-cresol) No. (parts by weight) days Stabilizer M =6 -(3,5-di-tert.butyl-4-hydroxy-phenyl)- l5 propionic acid stearate I t g stagilizer l;1 (Tlabllf llll) DLTDP; dilaurylthiodipropionate El a e t "1 Stabilizer II and Ill see Table l 7 l'l W (Table 43 I I 8 l stabilizer lll (Table l) 38 9 0.5 stabilizer II (Table l) 60 The results illustrate the superior effect of the stabi- "monllphenylphosph'le lizers of the invention.

EXAMPLE 3 EXAMPLE 5 Stabilization of an ABS Resin (40% Styrene 40% Stabilization of mineral Oil Acrylnitrile 20% Butadiene) In tests 10-14, 100 g each of a mineral oil were mixed with the stabilizers listed in Table V, and 5 liters of oxy- Mlxmres of 100 parts by weight of ABS wnh a Stab] gen were passed through the liquids for 90 minutes at lizer and 2 parts of l,2-bis-stearoyl-aminoethane as lu- 190C. The produced decomposition was determined bricant were rolled on a laboratory roller mill for 10 by the increased discoloration, measured by the Gard minutes at 160C, and the Obtamed films were Pressed ner color values, and by the increased viscosity. The

at a pressure of 200 atm. at a temperature of 180 to mineral oil itself at the start of the tests had a Gardner sheets of 1 mm thickness. Test specimens cut from said color value of 3-4, and at 20C a viscosity of 144 Cps.

0.05 trinonylphenyl phosphite 14 0.05 2,4,6 -tert.butyl phenol I2 I88 0.05 2.4 -dimethylphenol sheets were stored in a drying cabinet at 110C to pro- The table shows the good results obtained with the duce accelerating ageing, and the effect of the stabiliznovel slablllzeri Particularly when used together with a ers was determined by the discoloration and brittleness phosphlte' of the specimens. The results are given in Table Ill. EXAMPLE 6 TABLE III Stabilization of vegetable oils and plasticizers The same stabilizers as employed in Table V were me In Test Stabilizer Color after drying cabinet used in a sirn lar manner for a vegetable oil (olive oil) No. (parts by weight) 10 days b f becoming and a plasticizer (dioctylphthalate). The results were brittle (days) similar to those obtained with the mineral oil.

We claim: I 0.5 2,6-d 3 tyl phenol 7 l. A process of preparing (4-hydroxy-3,5-dialkyly benzyl) carboxylic acid esters of the formula eno 2 0.5 stabilizer L brown 42 3 0.5 stabilizer] light yellow 46 R (Table l) l 4 0.5 stabilizer Ill pale yellow 5] 0 H H iR,H-COOR (I) As the Table III shows, the stabilizers I and ll of the 3 invention exceed the stabilizing efficiency of the known stabilizers.

5 wherein EXAMPLE 4 R and R are alkyl groups at least one of which con- Stabilization of polyamides (Condensation products of tains l-6 carbon atoms, and

dicarboxylic acid and diamines) R is CN,

R being'a member of the group consisting of alkyl. thioether, and ether radicals, said radicals containing 1 to carbon atoms,

comprising reacting in an anhydrous organic solvent a Mannich base of the formula H H N(R)2 (II) in which R is lower alkyl, with a carboxylic acid ester of the formula -COOR R R R and R having the same significance as above in the presence of a catalytic amount of an alcohola'te of a metal selected from the group consisting of alkali metal and alkaline earth metals.

2. The process as claimed in claim 1 wherein said solvent is an'aromatic hydrocarbon.

3. The process as claimed in claim 1 wherein R and R,- are each alkyl groups containing 1-6 carbon atoms.

4. The process as claimed in claim 3 wherein at least one of R and R, is linked with a tertiary C-atom to th aromatic nucleus.

5. The process as claimed in claim 1 wherein the re-v action is conducted under reflux conditions. 

1. A PROCESS OF PREPARING (4-HYDROXY-3,5-DIALKYL-BENZYL) CARBOXYLIC ACID ESTERS OF THE FORMULA
 2. The process as claimed in claim 1 wherein said solvent is an aromatic hydrocarbon.
 3. The process as claimed in claim 1 wherein R1 and R2 are each alkyl groups containing 1-6 carbon atoms.
 4. The process as claimed in claim 3 wherein at least one of R1 and R2 is linked with a tertiary C-atom to the aromatic nucleus.
 5. The process as claimed in claim 1 wherein the reaction is conducted under reflux conditions. 